Method of manufacturing a composite vibrator

ABSTRACT

The present invention provides a composite vibrator that can maintain high sensitivity even when miniaturized. The composite vibrator includes tuning bar vibrators having the same length and support members for supporting the tuning bar vibrators. The tuning bar vibrators are arranged in a direction orthogonal to the longitudinal direction to be coupled with each other near nodes of bending vibrations occurring at both free ends of the tuning bar vibrators. In this arrangement, since the tuning bar vibrators are coupled with each other, the mass of the composite vibrator increases. Thus, even when the length of the longitudinal direction of the tuning bar vibrator is reduced, due to the increased mass, higher sensitivity for the detection of an angular velocity can be obtained.

This application is a Divisional of U.S. patent application Ser. No.10/008,759 filed Nov. 8, 2001 now U.S. Pat. No. 6,655,210.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to composite vibrators, vibration gyrosusing the vibrators, and electronic apparatuses incorporating thegyroscopes. In addition, the invention relates to methods ofmanufacturing the composite vibrators. More particularly, the inventionrelates to composite vibrators incorporated in video cameras with ashake preventing function, car navigation systems, pointing devices, orthe like, vibration gyroscopes using the vibrators, electronicapparatuses incorporating the vibration gyroscopes, and methods ofmanufacturing the composite vibrators.

2. Description of the Related Art

FIG. 22 shows a perspective view of a conventional vibration gyroscope.In this figure, a vibration gyroscope 60 includes a tuning bar vibrator600 and a frame 610. The turning bar vibrator 600 includes a firstpiezoelectric member 101 polarized in its thickness direction, with afirst electrode 104 a and a second electrode 104 b having the samedimensions being formed on a main surface thereof, a secondpiezoelectric member 102 polarized in its thickness direction, with athird electrode 105 formed on a main surface thereof, and conductivesupport members 106 a, 106 b, 106 c, and 106 d. The first electrode 104a and the second electrode 104 b are arranged in the longitudinaldirection of the tuning bar vibrator 600 at a predetermined distance inthe width direction. The other main surface of the first piezoelectricmember 101 is bonded to the other main surface of the secondpiezoelectric member 102 via an intermediate electrode 103. In each ofthe first and second piezoelectric members 101 and 102, a ratio betweenthe length L1 of the thickness direction and the length L2 of the widthdirection, that is, the value of L1/L2 is set to be approximately 1. Inthe tuning bar vibrator 600, in positions (near nodes N1 and N2) inwhich the nodes N1 and N2 (axes) of bending vibrations at both free endsin the thickness direction are projected perpendicularly to a mainsurface of the tuning bar vibrator 600, the support member 106 a isconnected to the first electrode 104 a, the support member 106 b isconnected to the second electrode 104 b, and the support members 106 cand 106 d are connected to the third electrode 105. The frame 610 ismade of resin and has a sufficiently large mass. The end portions of thesupport members 106 a, 106 b, 106 c, and 106 d are fixed to the frame610.

The vibration gyroscope 60 having the above structure performs bendingvibrations at both free ends when an excitation signal is applied to thethird electrode 105 via the support members 106 c and 106 d. The nodesobtained in the vibrations are N1 and N2 as axes orienting in the widthdirection of the vibration gyroscope 60. When there is applied anangular velocity whose rotational axis is the longitudinal direction ofthe tuning bar vibrator 600, the vibration gyroscope 60 performs bendingvibrations at both free ends in the width direction orthogonal to thedirection of excitation. The vibration nodes obtained in this case areN3 and N4 as axes orienting in the thickness direction substantially atthe center in the width direction of the vibration gyroscope 60. Signalsof bending in the width direction are output from the first electrode104 a and the second electrode 104 b.

In the vibration gyroscope 60, when the tuning bar vibrator 600 vibratesin the thickness direction and the width direction, the center ofgravity shifts. Then, the vibrations of the tuning bar vibrator 600partially leak to the outside frame 610 via the support members 106 a,106 b, 106 c, and 106 d. The frame 610 absorbs the vibrations leakingfrom the tuning bar vibrator 600.

Conventional vibration gyroscopes are described in Japanese UnexaminedPatent Application Publication No. 7-332988, and the like.

In general, a vibrator gyroscope requires miniaturization. Particularly,the length of the longitudinal direction of a tuning bar vibrator needsto be reduced, since the length is longer than the lengths of thewidthwise and thickness directions thereof. However, the sensitivity ofa vibration gyroscope is proportional to a given angular velocity, avibration velocity of a vibrator, and the mass of the vibrator. Thus,when the length of the longitudinal direction of the tuning bar vibratoris reduced, the mass of the composite vibrator decreases and thereby thesensitivity of the vibration gyroscope is deteriorated.

In addition, when the vibrations of the tuning bar vibrator leaksoutside, the amplitude of the vibrator is attenuated. As a result, thesensitivity of the vibration gyroscope is deteriorated.

In addition, due to the deteriorated sensitivity of the vibrationgyroscope, the ratio of noise with respect to signal increases.Furthermore, since the temperature characteristics of support membersand an acceleration detecting circuit become more influential, a valuedetected for an angular velocity tends to change.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide acomposite vibrator which can maintain high sensitivity even whenminiaturized.

In addition, it is another object of the invention to provide a methodof easily manufacturing the composite vibrator.

In addition, it is another object of the invention to provide avibration gyroscope using the composite vibrator, which can maintainhigh sensitivity even when miniaturized.

In addition, it is another object of the invention to provide anelectronic apparatus using the vibration gyroscope capable of accuratelydetecting an angular velocity to precisely control the angular velocity.

To this end, according to the present invention, there is provided acomposite vibrator including a plurality of tuning bar vibrators havingthe same length and support members for supporting the tuning barvibrators. In this composite vibrator, the tuning bar vibrators withboth ends free are arranged in a direction orthogonal to a longitudinaldirection of the tuning bar vibrators and are coupled with each other inthe vicinity of nodes of bending vibrations.

In addition, the plurality of tuning bar vibrators may include at leasttwo tuning bar vibrators having the same configuration.

In addition, each tuning bar vibrator may include an electrode to whicha signal for exciting the tuning bar vibrator is applied and anelectrode from which a signal corresponding to bending vibration of thetuning bar vibrator in a direction orthogonal to the direction ofexcitation is output.

In addition, adjacent tuning bar vibrators may be excited in mutuallyopposite directions.

In addition, a resonant frequency in the exciting direction of at leastone of the tuning bar vibrators may coincide with a resonant frequencyin the direction orthogonal to the exciting direction.

In addition, at least two electrodes formed in the longitudinaldirection of a main surface of each tuning bar vibrator may be arrangedat a predetermined distance in the width direction thereof.

According to the present invention, there is provided a vibrationgyroscope including a driving unit for driving the composite vibratorand a detecting unit for detecting an angular velocity via the compositevibrator.

Further there is provided an electronic apparatus including the abovevibration gyroscope.

There is provided a method of manufacturing a composite vibrator. Themethod includes a first step of bonding an auxiliary substrate to asecond main surface of a base substrate, a second step of completelycutting the base substrate from the direction of a first main-surfaceside of the base substrate while leaving a part of the auxiliarysubstrate to form a plurality of tuning bar vibrators arranged in awidth direction, the relative positions of the tuning bar vibratorsbeing retained by the auxiliary substrate, a third step of bondingsupport members to the first main surfaces of the tuning bar vibrators,and a fourth step of separating the auxiliary substrate from the secondmain surfaces of the tuning bar vibrators.

In addition, the base substrate may have electrodes formed on both mainsurfaces thereof.

In addition, the base substrate may be formed by bonding twopiezoelectric substrates polarized in mutually opposite directions withrespect to the thickness direction thereof.

Alternatively, the base substrate may be formed by bonding a conductivesubstrate to a piezoelectric substrate polarized in the thicknessdirection.

In addition, the second step may include forming grooves along one ofthe longitudinal and width directions on the first main surfaces of thetuning bar vibrators.

In addition, the third step may include bonding the support members inthe vicinity of nodes of bending vibrations of the tuning bar vibratorswith both ends free.

In addition, the composite vibrator manufacturing method may furtherinclude a fifth step of bonding support members to the nodes on thesecond main surfaces of the tuning bar vibrators after the first tofourth steps are performed.

In the above arrangement of the composite vibrator of the invention,since the plurality of tuning bar vibrators is coupled with each other,the mass of the composite vibrator increases. Thus, even when the lengthof the longitudinal direction is reduced, due to the increased mass, itssensitivity for the detection of an angular velocity is improved.

Additionally, in the composite vibrator of the invention, since thetuning bar vibrators are excited in mutually opposite directions to bebent in mutually opposite directions, the vibrations of the tuning barvibrators are trapped inside and thereby the vibrations hardly leakoutside. As a result, since loss caused by the leaked vibrations of thetuning bar vibrators decreases, the angular-velocity detectionsensitivity is improved.

In addition, since the vibration gyroscope of the invention uses thecomposite vibrator with high detection sensitivity, its angular-velocitydetection sensitivity is improved.

In addition, since the vibration gyroscope of the invention uses thecompact composite vibrator, miniaturization of the vibration gyroscopecan be achieved.

Furthermore, in the method of manufacturing the composite vibratoraccording to the invention, in the first step, the base substrate isbonded to the auxiliary substrate, and while keeping the bonding state,the second and third steps are sequentially performed. Thus, withoutcausing positional deviation of the tuning bar vibrators, the compositevibrator including the tuning bar vibrators having the sameconfiguration can be easily manufactured.

Furthermore, the electronic apparatus of the invention uses thevibration gyroscope capable of accurately detecting an angular velocitywith high sensitivity, a precise controlling mechanism can be formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a composite vibrator according to anembodiment of the present invention.

FIG. 2 is a plan view of the composite vibrator shown in FIG. 1.

FIG. 3 is a bottom view of the composite vibrator shown in FIG. 1.

FIG. 4 is a left side view of the composite vibrator shown in FIG. 1.

FIGS. 5A to 5C show perspective views illustrating the former proceduresin a method of manufacturing the composite vibrator shown in FIG. 1.

FIGS. 6A to 6C show perspective views illustrating the latter proceduresin the method.

FIG. 7 is a perspective view illustrating more details about a secondstep of the above method.

FIG. 8 is a plan view showing a state of vibrations of the compositevibrator shown in FIG. 1.

FIG. 9 is a front view showing a state of vibrations of the compositevibrator shown in FIG. 1.

FIGS. 10A and 10B illustrate analytical results of the vibrations of thecomposite vibrator obtained with the use of a finite element method.

FIG. 11 is a circuit block diagram of a vibration gyroscope according toan embodiment of the present invention.

FIG. 12 illustrates curves generated by dicing.

FIG. 13 is a circuit block diagram of a vibration gyroscope according toanother embodiment of the present invention.

FIG. 14 is a plan view of a composite vibrator according to anotherembodiment of the present invention.

FIG. 15 is a circuit block diagram of a vibration gyroscope according toanother embodiment of the present invention.

FIG. 16 is a circuit block diagram of a vibration gyroscope according toanother embodiment of the present invention.

FIG. 17 is a circuit block diagram of a vibration gyroscope according toanother embodiment of the present invention.

FIG. 18 is a left side view of a composite vibrator according to anotherembodiment of the invention.

FIG. 19 is a plan view showing the performance of the composite vibratorshown in FIG. 18.

FIG. 20 is a front view showing the performance of the compositevibrator shown in FIG. 18.

FIG. 21 is a block diagram of a shake preventing circuit used in anelectronic apparatus according to an embodiment of the invention.

FIG. 22 is a perspective view of a conventional vibration gyroscope.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Each of FIGS. 1 to 4 shows a composite vibrator according to anembodiment of the present invention. FIG. 1 is a perspective view of thecomposite vibrator, FIG. 2 is a plan view thereof, FIG. 3 is a bottomview thereof, and FIG. 4 is a left side view thereof. In FIGS. 1 to 4,the reference numerals used in the vibration gyroscope 60 shown in FIG.22 are given to the same and equivalent parts shown in the figures, andthe explanation of the parts will be omitted.

In each of FIGS. 1 to 4, a composite vibrator 10 of the invention is avibrator used in a vibration gyroscope and includes two tuning barvibrators 100 and 200 having the same length and sectional dimensionsand support members 106 a, 106 b, 106 c, and 106 d for supporting thetuning bar vibrators 100 and 200. The tuning bar vibrators 100 and 200are made of the same material as that of the tuning bar vibrator 600shown in FIG. 22 and are polarized in the same directions indicated byarrows shown in FIG. 4. A ratio between the length L1 of a thicknessdirection of each vibrator and the length L2 of a width directionthereof, that is, the value of L1/L2, is set to be approximately 0.8.This is the only part different from the structure of the tuning barvibrator 600. The tuning bar vibrators 100 and 200 are arranged in adirection orthogonal to the longitudinal directions thereof. Then, nearpositions in which positions (axes) as nodes N1 and N2 of bendingvibrations in the thickness direction at both free ends of the tuningbar vibrators are projected perpendicularly to main surfaces of thetuning bar vibrators 100 and 200, the tuning bar vibrators 100 and 200are coupled with each other via the support members 106 a, 106 b, 106 c,and 106 d.

Here, first, a description will be given of a method of manufacturingthe composite vibrator of the invention with reference to FIGS. 5A to 5Cand FIGS. 6A to 6C. In this method, first to fifth steps will beperformed as follows.

As shown in FIG. 5A, first, there is provided a base substrate 300formed by bonding a first piezoelectric substrate 310 polarized in athickness direction and a second piezoelectric substrate 320 polarizedin a thickness direction opposed to the first piezoelectric substrate310 via an electrode 300. An electrode 311 is formed on a first mainsurface of the base substrate 300 and an electrode 321 is formed on asecond main surface thereof.

In the first step of the method of manufacturing the composite vibratoraccording to the present invention, as shown in FIG. 5B, an auxiliarysubstrate 400 made of resin is bonded to the second main surface of thebase substrate 300 with an adhesive.

In the second step, as shown in FIG. 5C, the base substrate 300 iscompletely cut from the direction of the first main-surface side thereofby a dicer or the like to form tuning bar vibrators 100 and 200 arrangedin a width direction, while leaving a part of the auxiliary substrate400. This arrangement retains the positions of the tuning bar vibrators100 and 200 adjacent to each other in the width direction via theauxiliary substrate 400. Furthermore, on first main surfaces of thetuning bar vibrators 100 and 200, deep grooves 107 are formed in thelongitudinal directions of the tuning bar vibrators and shallow grooves108 are formed in the width directions thereof to form first electrodes104 a and 204 a and second electrodes 104 b and 204 b. The deep grooves107 are formed by digging into parts of the first piezoelectricsubstrate 310 and the shallow grooves 108 are formed by cutting only theelectrode 311. For example, the electrode 311 is cut by a laser or thelike.

In the third step, as shown in FIG. 6A, support members 106 a and 106 bare bonded to the first main surfaces of the tuning bar vibrators 100and 200.

In the fourth step, the auxiliary substrate 400 and the tuning barvibrators 100 and 200 are soaked into a parting agent. Then, as shown inFIG. 6B, the auxiliary substrate 400 is separated from the second mainsurfaces of the tuning bar vibrators 100 and 200. Sequentially, theshallow grooves 108 (not shown) are formed into the electrodes 311 ofthe tuning bar vibrators 100 and 200 in the width directions to formthird electrodes 105 and 205 (not shown).

In the fifth step, as shown in FIG. 6C, support members 106 c and 106 dare bonded to the tuning bar vibrators 100 and 200.

In this method, as described above, in the first step, the basesubstrate 300 is bonded to the auxiliary substrate 400, and whilemaintaining the bonding state, the first and third steps aresequentially performed. Thus, the support members 106 a and 106 b can bedisposed without causing deviations in the relative positions of thetuning bar vibrators 100 and 200 having the same configuration.

Furthermore, in the fifth step, in the state in which the supportmembers 106 a and 106 b are bonded to the tuning bar vibrators 100 and200, the support members 106 c and 106 d are bonded. Thus, withoutcausing any positional deviation in the tuning bar vibrators 100 and200, the composite vibrator 10 can be easily manufactured.

As shown in FIG. 7, in the second step of the method, alternatively, inthe state in which the base substrate 300 is partially bonded to theauxiliary substrate 400, the base substrate may be split into two ormore tuning bar vibrators 100 and 200. In addition, the base substrateused in the method of manufacturing the composite vibrator of theinvention may be a substrate formed by bonding piezoelectric substratespolarized in the width directions thereof or bonding a conductivesubstrate to a piezoelectric substrate.

Next, referring to FIGS. 8 and 9, a description will be given of theperformance of the composite vibrator 10 according to the invention.FIG. 8 shows a plan view of a state of the vibrations of the compositevibrator 10 and FIG. 9 shows a front view of a state of the vibrationsthereof.

In the composite vibrator 10 shown in each of FIGS. 8 and 9, anexcitation signal is applied between the first and second electrodes 104a and 204 b connected to the support member 106 a and the first andsecond electrodes 204 a and 104 b connected to the support member 106 b.Then, the tuning bar vibrators 100 and 200 are excited in mutuallyopposite directions and then perform free end bending vibrations in thewidth direction, in which nodes of the vibrations are N3 and N4, whichare symmetrical to the width direction of the composite vibrator 10 andare axes orienting in the thickness directions substantially at thecenters in the width directions of the tuning bar vibrators 100 and 200.Hereinafter, the mode of such bending vibrations in the width directionsmode will be referred to as A mode.

When there is given an angular velocity whose rotational axis is thelongitudinal direction of the composite vibrator 10, the tuning barvibrators 100 and 200 perform bending vibrations in mutually oppositedirections, that is, they perform bending vibrations at both free endsin the thickness direction, in which the vibrators 100 and 200 vibratein mutually opposite directions in the thickness direction of thecomposite vibrator 10, and nodes of the vibrations are N1 and N2.Hereinafter, the mode of such bending vibrations in the thicknessdirection will be referred to as B mode. Signals corresponding tobending vibrations in the thickness direction are output from the thirdelectrodes 105 and 205 via the support members 106 c and 106 d.

In the composite vibrator 10 having the above structure, since the twotuning bar vibrators 100 and 200 are coupled with each other, the massof the composite vibrator 10 increases. Therefore, even when the lengthof the longitudinal direction is reduced, due to the increased mass, thesensitivity for the detection of an angular velocity is improved. Evenif the lengths of the longitudinal directions of the tuning barvibrators 100 and 200 are halved, basically, the detection sensitivityis not reduced.

In addition, in the composite vibrator 10 of the invention, unlike acase in which the tuning bar vibrators 100 and 200 are supported inpositions other than the nodes thereof, the tuning bar vibrators 100 and200 are supported at the nodes N1, N2, N3, and N4 or near these nodes.Thus, bending vibrations occurring at both free ends of the tuning barvibrators 100 and 200 are not hindered and the angular-velocitydetection sensitivity is hardly deteriorated.

In the composite vibrator 10, since the tuning bar vibrators 100 and 200are excited in mutually opposite directions to be bent in mutuallyopposite directions, vibration energy of the tuning bar vibrators 100and 200 is trapped inside and thereby the vibrations hardly leakoutside. In other words, in the composite vibrator 10, since the tuningbar vibrators 100 and 200 vibrate in the mutually opposite directions,the center of gravity in the composite vibrator 10 is always maintainedbetween the tuning bar vibrators 100 and 200 without shifting. As aresult, the vibrations of the tuning bar vibrators 100 and 200 hardlyleak outside. Thus, since loss caused by vibration leakage of the tuningbar vibrators 100 and 200 decreases, the angular-velocity detectionsensitivity can be improved. Particularly, the vibrations in the widthdirection are excitation vibrations with large amplitude. Thus, when thevibration leakage is reduced, the angular-velocity detection sensitivityis significantly improved.

Next, FIGS. 10A and 10B illustrate analytical results regarding thevibrations of a composite vibrator obtained based on a finite elementmethod. Here, a more detailed explanation will be given of the resonantfrequency of the composite vibrator. FIG. 10A shows results about anA-mode excitation state of the composite vibrator analyzed by the finiteelement method. FIG. 10B shows results about a B-mode bending state ofthe composite vibrator analyzed by the same method. Each of FIGS. 10Aand 10B illustrates the half side of the composite vibrator in thelongitudinal direction. The only point different from the structure ofthe composite vibrator 10 is that a ratio between the length L1 of thethickness direction and the length L2 of the width direction is set tobe approximately 1.

In FIG. 10, when the composite vibrator is excited at the A mode, theresonant frequency of bending vibrations in the width direction is 22.73kHz, and when the vibrator is bent at the B mode, the resonant frequencyof bending vibrations in the thickness direction is 28.05 kHz. Thus, theresonant frequency in the thickness direction is higher than theresonant frequency in the width direction. As shown here, when theresonant frequency in the thickness direction does not coincide with theresonant frequency in the width direction, the efficiency of vibrationsis deteriorated and thereby the sensitivity for the detection of anangular velocity is reduced.

Therefore, in the composite vibrator 10 of the present invention, onlythe resonant frequency of bending vibrations in the thickness directionbecomes lower by reducing the length of the thickness direction. Inother words, in the composite vibrator 10, the ratio between the lengthL1 of the thickness direction and the length L2 of the width direction,that is, the value of L1/L2, is set to be 22.73 kHz/28.05 kHz (whichequals to approximately 0.8), and the resonant frequency in thethickness direction is set to be 22.73 kHz, which is the same as theresonant frequency in the width direction. As shown here, in thecomposite vibrator 10, since the resonant frequency in the thicknessdirection coincides with the resonant frequency in the width direction,vibration efficiency is increased and thereby the angular-velocitydetection sensitivity is improved.

Next, FIG. 11 shows a circuit block diagram of a vibration gyroscope 20using the composite vibrator 10 according to an embodiment of theinvention. In each of FIGS. 11, 13, and 15 to 17, support members willnot be shown.

In FIG. 11, the vibration gyroscope 20 includes the composite vibrator10 shown in FIG. 1, an oscillating circuit 610 as a driving unit, and adetecting circuit 620 as a detecting unit. The oscillating circuit 610includes an AGC circuit 611 and a phase correcting circuit 612 connectedto the AGC circuit 611. The detecting circuit 620 includes a firstdetecting circuit 621, a second detecting circuit 622, a differentialcircuit 623 connected to the first detecting circuit 621 and the seconddetecting circuit 622, a detector circuit 624 connected to thedifferential circuit 623 and the phase correcting circuit 612, asmoothing circuit 625 connected to the detector circuit 624, and anamplifier circuit 626 connected to the smoothing circuit 625.

In the composite vibrator 10 of the vibration gyroscope 20, the firstelectrode 204 a and the second electrode 104 b are connected to the AGCcircuit 611 via the support member 106 b (not shown). The thirdelectrode 105 is connected to the first detecting circuit 621 via thesupport member 106 c (not shown). The third electrode 205 is connectedto the second detecting circuit 622 via the support member 106 d (notshown). In addition, the output of the phase correcting circuit 612 isconnected to the first electrode 104 a and the second electrode 204 bvia the support member 106 a (not shown).

In the vibration gyroscope 20 having the above structure, the AGCcircuit 611 makes the amplitude of a signal input from each of thesecond electrode 104 b and the first electrode 204 a constant to outputthe signal to the phase correcting circuit 612. The phase correctingcircuit 612 corrects the phase of the input signal to apply a drivingsignal to each of the first electrode 104 a and the second electrode 204b. The first detecting circuit 621 and the second detecting circuit 622output the voltages of the third electrodes 105 and 205 to thedifferential circuit 623, which performs the subtraction of the inputsignal to output to the detector circuit 624. The detector circuit 624detects the signal input from the differential circuit 623 with the useof an signal input from the phase correcting circuit 612 to output tothe smoothing circuit 625. The smoothing circuit 625 smoothes the inputsignal to output to the amplifier circuit 626, which performs the DCamplification of the input signal to output the signal as anangular-velocity signal outside.

In the vibration gyro 20 having the above structure, due to theincreased mass of the composite vibrator 10, the angular-velocitydetection sensitivity is improved.

In addition, since the vibration gyro 20 uses the compact compositevibrator 10, the vibration gyroscope can be miniaturized.

In addition, the vibration gyro 20 uses the composite vibrator 10 havinghigh detection sensitivity, the angular-velocity detection sensitivityis improved.

Furthermore, in the vibration gyro 20, the oscillating circuit 610 isnot directly connected to the detecting circuit 620 and these circuitsare independent from each other. Thus, the gain of the oscillatingcircuit 610 and the gain of the detecting circuit 620 can be designedindependently. As a result, without being influenced by the oscillatingcircuit 610, the gain of the detecting circuit 620 can be increased andthereby the angular-velocity detection can be performed with highprecision.

Furthermore, in the vibration gyro 20, since the mass of the compositevibrator 10 becomes large, the sensitivity of signals output from thethird electrodes 105 and 205 is improved. As a result, the detectingcircuit 620 can be formed by using the amplifier circuit 626 having asmall amplification rate. This can reduce circuit cost.

When the deep grooves 107 are formed in the tuning bar vibrators 100 and200, there are generated curves 107 a as shown in FIG. 12. Such a curvetends to be generated when the tuning bar vibrators 100 and 200 arediced by a diamond wheel. In this case, due to stress applied only onone side of the part, size reduction becomes unbalanced. In theconventional vibration gyro 60, due to the curves generated, thedimensions of the first electrodes 104 a and 204 a or the secondelectrodes 104 b and 204 b are reduced. Thus, capacitance andpiezoelectric performance capabilities become unbalanced between theelectrodes having reduced dimensions and the electrodes maintaining thesame dimensions. As a result, accurate angular-velocity detection cannotbe performed.

In the vibration gyroscope 20 of the invention, the tuning bar vibrators100 and 200 are polarized in the same direction, the second electrode104 b is connected to the first electrode 204 a, and the first electrode104 a is connected to the second electrode 204 b. Thus, in the vibrationgyroscope 20, in the case of the formation of the deep grooves 107, evenwhen the curves 107 a are generated and thereby the dimensions of thefirst electrodes 104 a and 204 a or the dimensions of the secondelectrodes 104 b and 204 b are reduced, the balance is achieved in thecapacitance and piezoelectric performance capabilities between the firstand second electrodes 104 a and 204 b and the first and secondelectrodes 204 a and 104 b.

Next, FIG. 13 shows a circuit block diagram of a vibration gyroscopeusing the composite vibrator 10 according to another embodiment of theinvention.

In FIG. 13, a vibration gyroscope 20 a includes an oscillating circuit610 a as an alternative to the oscillating circuit 610 of the vibrationgyroscope 20 shown in FIG. 11.

The oscillating circuit 610 a includes, in addition to the structure ofthe oscillating circuit 610, a first detecting circuit 621, a seconddetecting circuit 622, and an adding circuit 613. The oscillatingcircuit 610 a is different from the oscillating circuit 610 in the onlyone point that the adding circuit 613 is connected to the firstdetecting circuit 621 and the second detecting circuit 622.

In the composite vibrator 10 of the vibration gyroscope 20 a, the firstelectrode 204 a and the second electrode 104 b are grounded. The firstelectrode 104 a and the second electrode 204 b are connected to thephase correcting circuit 612. The third electrode 105 is connected tothe first detecting circuit 621 and the third electrode 205 is connectedto the second detecting circuit 622. The adding circuit 613 of thevibration gyroscope 20 performs the addition of signals output from thefirst detecting circuit 621 and the second detecting circuit 622 tooutput to the AGC circuit 611.

In the vibration gyroscope 20 a having the above structure, thecomposite vibrator 10 is excited at the A mode, and when an angularvelocity is applied, the vibrator 10 is bent at the B mode to output asignal corresponding to the angular velocity. In actual vibrations,since the first electrode 204 a and the second electrode 104 b aregrounded, the composite vibrator 10 is excited in directions indicatedby arrows, being deviated from the A mode. When an angular velocity isapplied, the vibrator 10 is bent in a direction orthogonal to theexciting direction.

The vibration gyroscope 20 a having the above structure can also obtainthe same advantages as those obtained in the vibration gyroscope 20.

Next, FIG. 14 shows a plan view of a composite vibrator according toanother embodiment of the invention. FIG. 15 shows a circuit blockdiagram of a vibration gyroscope using the composite vibrator shown inFIG. 14, according to another embodiment of the invention.

In FIG. 14, a composite vibrator 10 a has support members 106 e and 106f as alternatives to the support member 106 a. This is the only onepoint different from the structure of the composite vibrator 10. Thesupport member 106 e is connected to the first electrode 104 a and thesupport member 106 f is connected to the second electrode 204 b. Likethe support member 106 a, the support members 106 e and 106 f supportthe tuning bar vibrators 100 and 200 and serve as leads.

In FIG. 15, instead of the composite vibrator 10 of the vibrationgyroscope 20 shown in FIG. 11, a vibration gyroscope 20 b includes thecomposite vibrator 10 a. Additionally, in the composite vibrator 10 a ofthe vibration gyroscope 20 b, the first electrode 104 a is connected tothe AGC circuit 611 via the support member 106 e (not shown). The secondelectrode 204 b is connected to the phase correcting circuit 612 via thesupport member 106 f (not shown). The first electrode 204 a and thesecond electrode 104 b are grounded. The third electrode 105 isconnected to the first detecting circuit 621 and the third electrode 205is connected to the second detecting circuit 622.

In the vibration gyroscope 20 b having the above structure, thecomposite vibrator 10 is excited at the A mode, and when an angularvelocity is applied, the vibrator 10 is bent at the B mode and a signalcorresponding to the angular velocity is output.

The vibration gyroscope 20 b can also obtain the same advantages asthose obtained in the vibration gyroscope 20.

Next, FIG. 16 shows a circuit block diagram of a vibration gyroscopeusing the composite vibrator of the invention, according to anotherembodiment of the invention.

In FIG. 16, a vibration gyroscope 20 c of the invention includes thecomposite vibrator 10 a as an alternative to the composite vibrator 10of the vibration gyroscope 20 a shown in FIG. 13.

In the composite vibrator 10 a of the vibration gyroscope 20 c, thefirst electrode 104 a is connected to the second detecting circuit 622and the second electrode 204 b is connected to the first detectingcircuit 621. The first electrode 204 a and the second electrode 104 bare connected to the phase correcting circuit 612. The third electrodes105 and 205 are grounded.

In the vibration gyroscope 20 c having the above structure, thecomposite vibrator 10 a is excited at the A mode, and when an angularvelocity is applied, the vibrator 10 a is bent at the B mode. Then, asignal corresponding to the angular velocity is output.

The vibration gyroscope 20 c can also obtain the same advantages asthose obtained in the vibration gyroscope 20.

In the vibration gyroscope 20 c, the third electrodes 105 and 205 havethe same potential. Thus, on the main surface on which the thirdelectrodes 105 and 205 are formed, instead of forming the shallowgrooves 108 shown in FIG. 3, the support members 106 c and 106 d may beconnected to the third electrodes 105 and 205.

Next, FIG. 17 shows a circuit block diagram of a vibration gyroscopeusing the composite vibrator of the invention, according to anotherembodiment of the invention.

In FIG. 17, a vibration gyroscope 20 d of the invention includes thecomposite vibrator 10 a as an alternative to the composite vibrator 10of the vibration gyroscope 20 shown in FIG. 11.

In the composite vibrator 10 a of the vibration gyroscope 20 d, thefirst electrode 104 a is connected to the second detecting circuit 622and the second electrode 204 b is connected to the first detectingcircuit 621. The first electrode 204 a and the second electrode 104 bare grounded. The third electrode 105 is connected to the AGC circuit611 and the third electrode 205 is connected to the phase correctingcircuit 612.

In the vibration gyroscope 20 d having the above structure, thecomposite vibrator 10 a is excited at the B mode, and when an angularvelocity is applied, the vibrator 10 a is bent at the A mode and then asignal corresponding to the angular velocity is output.

The vibration gyroscope 20 d can also obtain the same advantages asthose obtained in the vibration gyroscope 20.

In each of the above embodiments, the first detecting circuit and thesecond detecting circuit may be a current detecting circuit, a voltagedetecting circuit, a capacitance detecting circuit, a buffer circuit, anon-inverting amplifier, an inverting amplifier, or the like.

Next, FIG. 18 shows a left side view of a composite vibrator accordingto another embodiment of the invention. FIGS. 19 and 20 show a plan viewand a front view illustrating the performance of a composite vibrator30.

In each of FIGS. 18 to 20, unlike the composite vibrator 10, thecomposite vibrator 30 includes tuning bar vibrators 100′ and 200′ asalternatives to the tuning bar vibrators 100 and 200 of the compositevibrator 10 shown in FIG. 4. In addition, in the composite vibrator 30,the first electrodes 104 a and 204 a, and the second electrodes 104 band 204 b are connected in a manner different from that in the compositevibrator 10.

The tuning bar vibrators 100′ and 200′ of the composite vibrator 30 arepolarized in mutually opposite directions as indicated by arrows shownin FIG. 18. Then, the first electrodes 104 a and 204 a are connected tothe support member 106 a and the second electrodes 104 b and 204 b areconnected to the support member 106 b.

In the composite vibrator 30 having the above structure, with theoscillating circuit 610 shown in FIG. 11, an exciting signal is appliedbetween the first electrodes 104 a and 204 a connected to the supportmember 106 a and the second electrodes 104 b and 204 b connected to thesupport member 106 b to excite the composite vibrator 30 at the A modeas shown in FIG. 19.

When an angular velocity, whose rotational axis is the longitudinaldirection of the composite vibrator 30, is applied to the compositevibrator 30, the composite vibrator 30 performs bending vibrations atthe B mode as shown in FIG. 20. A signal corresponding to the bendingvibrations is output from each of the third electrodes 105 and 205 viathe support members 106 c and 106 d. The signal output from each of thethird electrodes 105 and 205 is processed by a detecting circuit (notshown), in which the differential circuit 623 of the detecting circuit620 shown in FIG. 11 is replaced by a cumulative circuit.

In the composite vibrator 30, when curves as shown in FIG. 12 aregenerated due to the formation of the deep grooves 107, capacitance andpiezoelectric performance capabilities become unbalanced and thereby theaccuracy of angular-velocity detection is deteriorated. However, inother respects, the composite vibrator 30 can provide the sameadvantages as those obtained in the composite vibrator 10.

In each of the above embodiments, instead of the tuning bar vibrators100, 200, 100′, and 200′, there may be used tuning bar vibrators havingthree or more electrodes formed on first main surfaces thereof. Even inthis case, the composite vibrator can provide the same advantages asthose obtained in the composite vibrator 10. Furthermore, the compositevibrator of the invention may be formed by using tuning bar vibrators inwhich piezoelectric members are bonded to metal pieces. In this case,also, the composite vibrator can provide the same advantages as thoseobtained in the composite vibrator 10.

In each of the embodiments, the composite vibrator of the inventionincludes the support members 106 a, 106 b, 106 c, and 106 d. However,even with only the use of one of the support member 106 a or 106 c andone of the support member 106 b or 106 d, there can be provided the sameadvantages as those obtained in the composite vibrator 10.

Furthermore, in some of the above embodiments, the composite vibrator ofthe invention is excited at an excitation mode of the composite vibratorusing the two tuning bar vibrators, that is, at the A mode. Then, whenan angular velocity is applied, the composite vibrator vibrates at the Bmode. In other cases, the composite vibrator of the invention is excitedat the B mode, and when an angular velocity is applied, it is excited atthe A mode. Vibration modes applicable to the present invention are notrestricted to the modes of the above embodiments. For example, thevibration mode of a composite vibrator using three or more tuning barvibrators may be used.

Next, FIG. 21 shows an electronic apparatus using the vibrationgyroscope of the invention, according to an embodiment of the invention.FIG. 21 is a block diagram of a shake preventing circuit used in a videocamera, as one example of the electronic apparatus of the invention. Ashake preventing circuit 80 includes the vibration gyroscope 20, anintegrating circuit 801, a servo circuit 802, a current driver 803, anactuator 804, and a position detecting sensor 805. In the shakepreventing circuit 80, the vibration gyroscope 20, the integratingcircuit 801, the servo circuit 802, the current driver 803, and theactuator 804 are connected in series. An output feedback from theactuator 804 is given to the servo circuit 802 via the positiondetecting sensor 805.

In the shake preventing circuit 80 having the above structure, regardingshake given to a video camera, only the angular velocity is input fromthe vibration gyroscope 20 to the integrating circuit 801. Theintegrating circuit 801 integrates the angular-velocity signal toconvert into a shake angle of the video camera and output the signal tothe servo circuit 802. The servo circuit 802 uses the shake angle signalinput from the integrating circuit 801 and a signal from the positiondetecting sensor 805 to calculate the difference between the presentvalue and a target value and outputs the result to the current driver803. The current driver 803 outputs a current corresponding to the inputsignal to the actuator 804. The actuator 804 mechanically drives theoptical system of the video camera. Then, the position detecting sensor805 outputs the signal of a shake angle driving the optical system tothe servo circuit 802.

The video camera having the above structure, as the electronic apparatusaccording to the invention, incorporates the vibration gyroscope capableof accurately detecting an angular velocity with high sensitivity. Thus,the influence of shake can be appropriately prevented.

Although the embodiment of the electronic apparatus of the invention hasbeen described by using the video camera, the electronic apparatus ofthe invention is not restricted to the video camera having the abovestructure.

As described above, in the composite vibrator of the invention, thetuning bar vibrators are coupled with each other. Thus, even whenlengths of the longitudinal directions of the tuning bar vibrators arereduced, due to the increased mass, the sensitivity for the detection ofan angular velocity is improved.

In addition, in the composite vibrator of the invention, the tuning barvibrators are excited in mutually opposite directions to be bent inmutually opposite directions. Thus, vibrations of the tuning barvibrators are trapped inside and thereby the vibrations hardly leakoutside. As a result, since loss caused by leakage of the vibrations ofthe tuning bar vibrators is reduced, the angular-velocity detectionsensitivity is improved.

Furthermore, since the vibration gyroscope of the invention uses thecomposite vibrator with high detection sensitivity, the angular-velocitydetection sensitivity is improved.

In addition, since the vibration gyroscope of the invention uses thecompact composite vibrator, the vibrator gyroscope can be miniaturized.

In addition, in the method of manufacturing the composite vibrator ofthe invention, in the first step, the base substrate is bonded to theauxiliary substrate, and while maintaining the bonding state, the secondto fourth steps are sequentially performed. Thus, the positionaldeviations of the tuning bar vibrators are prevented. As a result, thecomposite vibrator including the tuning bar vibrators having the sameconfiguration can be easily manufactured.

The electronic apparatus of the invention uses the vibration gyroscopecapable of accurately detecting an angular velocity with highsensitivity. Thus, a precise control mechanism can be formed.

While preferred embodiments of the invention have been described above,variations and modifications thereto will occur to those skilled in theart within the scope of the present invention. The scope of theinvention, therefore, is to be determined solely by the followingclaims.

What is claimed is:
 1. A method of manufacturing a composite vibratorcomprising: a first step of bonding an auxiliary substrate to a secondmain surface of a base substrate; a second step of completely cuttingthe base substrate from the direction of a first main-surface side ofthe base substrate while leaving a part of the auxiliary substrate toform a plurality of tuning bar vibrators arranged in a width direction,the relative positions of the tuning bar vibrators being retained by theauxiliary substrate; a third step of bonding support members to thefirst main surface of the tuning bar vibrators; and a fourth step ofseparating the auxiliary substrate from the second main surfaces of thetuning bar vibrators.
 2. The method of manufacturing a compositevibrator according to claim 1, wherein the base substrate has electrodesformed on both main surfaces thereof.
 3. The method of manufacturing acomposite vibrator according to claim 1, wherein the base substrate isformed by bonding two piezoelectric substrates polarized in mutuallyopposite directions with respect to the thickness direction thereof. 4.The method of manufacturing a composite vibrator according to claim 1,wherein the base substrate is formed by bonding a conductive substrateto a piezoelectric substrate polarized in the thickness direction. 5.The method of manufacturing a composite vibrator according to claim 1,wherein the second step includes forming grooves along one of thelongitudinal and width directions on the first main surfaces of thetuning bar vibrators.
 6. The method of manufacturing a compositevibrator according to claim 1, wherein the third step includes bondingthe support members in the vicinity of nodes of bending vibrations ofthe tuning bar vibrators with both ends free.
 7. The method ofmanufacturing a composite vibrator according to claim 1, furthercomprising a fifth step of bonding support members to the nodes on thesecond main surfaces of the tuning bar vibrators after the first tofourth steps are performed.